Irrigation control

Abstract

An automatic irrigation control includes a pilot needle valve with a slidable stem and a block of material the dimensions of which change when exposed to moisture, arranged in a framework so that when the block expands it bears against the valve stem, closing the valve and shutting off a connected hydraulic valve. Preferably, an override lever, connected to a temperature-responsive device, is interposed between the block and the valve in such a way that when the temperature is above a predetermined height, the lever overrides the block and prevents the actuation of the hydraulic valve when the temperature is too high. An adjustable canopy regulates the rate of drying and wetting of the block.

I claim: 
     
       1. In an irrigation system in which earth is sprinkled with water falling upon it, a control system comprising a block frame; a needle valve mounted on said frame, said needle valve having a sliding stem projecting from it; biasing means for biasing said stem toward valve opening position; a two ended, elongated block of material that expands as it becomes wet and contracts as it dries, said block having upper and lower broad faces and relatively narrow side and end faces, mounted in said frame, being exposed and in contact, along the full length of its lower broad face, with part of the earth being watered and exposed along its upper broad face to the ambient air; adjustment means at one end of said block for moving said block toward and away from said needle valve; lever means positioned between the other end of said block and said sliding valve stem and operatively connected to said valve stem, said lever having a fulcrum intermediate its ends around which said lever rocks; a rod operatively connected to said lever on the opposite end of said lever, with respect to said fulcrum, from said block and valve stem, and support means for supporting said rod, said support means having a different temperature coefficient of expansion from said rod, whereby heating of said rod and support means causes said lever to rock about its fulcrum to move the valve stem, against its biasing means, to a valve closed position. 
     
     
       2. The control system of claim 1 including a canopy extending over the full length and width of said upper surface of said block, and means for adjusting the position of said canopy with respect to said block.